And Then There Were Three Tails
by Supervillegirl
Summary: Part 5 of my Tail series. Sherlock and John find a new merperson.


And Then There Were Three Tails

It all started when Mycroft demanded that he work a case for the government, reminding him that he owed him a favor for all the work he had done to keep his and John's secret. Begrudgingly, Sherlock had agree, but when Mycroft had told him it would be an undercover assignment in Germany, he had immediately hated it. And when John had told him he was needed in Attleborough for a family emergency, he was even less pleased, if that was possible. In order to have a convincing undercover story, he needed to be traveling with someone. This left Molly Hooper.

It was always going to be hard enough keeping his secret from Molly—especially since Mycroft's cover for them was as a Honeymooning couple and therefore were given one hotel room to share—but the mission itself had turned sideways. Somehow, it had completely slipped past Mycroft that this faction was holding prisoners. Now, they were forced to alter the plan to save them.

Sherlock led Molly around the corner, pausing as some guards ran past in the adjoining corridor in pursuit of the diversion they had caused. When the coast was clear, they turned down that hallway and reached a door that seemed to be triple-locked.

"Damn," he hissed as he knelt in front of it and yanked his lock-picking set out of his pocket.

 _If John had been here, I could have just busted it open,_ he thought.

He got the first two locks undone as Molly kept watch. But the third was proving unusually tricky.

"Sherlock…" Molly hissed urgently as voices sounded through the corridors.

 _Bugger it!_ Sherlock thought as he shielded the lock and his hands from Molly's view. He felt for the locking mechanism with his telekinesis and opened it. Pocketing the lockpicks, he stood and quickly opened the door, pulling Moly inside and closing it.

They turned and found the five hostages chained together in the corner. Sherlock looked around and quickly figured out where the keys were kept. Giving them to Molly, he found a pair of bolt cutters and started cutting through the chains. Molly had gotten the cuffs off of three of them before an explosion went off in the building. The room shook as the hostages screamed. Crates toppled off their piles, windows shattered, and a section of the ceiling above them cracked.

Molly looked up at Sherlock. "They found our decoy."

Abandoning the keys, Molly started helping the hostages out as Sherlock cut the last of the chains keeping the last two at the wall. Sherlock pulled them to their feet and followed Molly towards the door. A bang echoed through the room, and Sherlock pulled the woman in front of him back as pieces of the ceiling broke off and crashed to the floor. The other hostage he had freed was not so lucky. Her head took a hit from a piece of concrete, and she went to the floor, unconscious. A huge section of the metal and concrete ceiling now hung precariously from the ceiling directly over her. If he couldn't get her moved in time…

Sherlock glanced up at Molly, ushering the woman towards her. "Go with the others."

"What about—" Molly began with a worried look.

"I'll be right behind you," Sherlock told her firmly. "Go."

Molly glanced hesitantly up at the crumbling ceiling.

"Go!" Sherlock ordered.

Molly turned and ran with the hostages out of the room.

 _CRACK!_

Sherlock spun back towards the unconscious woman, throwing his hands up to catch the huge slab of concrete. It stopped in the air four feet from the woman. Sherlock concentrated, his hands starting to shake—it was so heavy—as he forced the slab further into the air. It was taking all his power to keep the slab floating, and he began to wonder how he would move the woman.

The sound of a soft gasp behind him had his heart hammering.

Sherlock looked over at the doorway back to his right. Molly stood there, staring with amazed eyes at him and the floating slab. Sherlock's eyes widened at the sight of her. How could he have been so stupid? John had managed to keep his secret for years, and Sherlock couldn't even make it a few months?

 _BANG!_

Sherlock turned back to see a steel beam break away from the wall and come toppling towards the woman on the floor. Not even sure how he would manage to catch it while keeping the concrete afloat, he prepared himself to do so. But the next second, the beam came to a stop in midair. Sherlock frowned and looked back at Molly.

Molly had her hand held out toward the beam, brow furrowed in concentration.

Sherlock's jaw practically dropped. _She's a mermaid…_

Molly's gaze moved to him, and Sherlock realized in that moment that when Molly had found him using telekinesis, there had been no confusion. She hadn't been shocked that something like this could happen. She had been amazed that _he_ was the one doing it.

There was a great screech, and Sherlock immediately moved his attention back to the slab.

"Go get her," Sherlock told her in a strained voice.

"You can't hold them both by yourself," Molly argued.

With a great groan of effort, Sherlock shifted his focus slightly, taking control of the beam as well. "Go!"

His arms shook with the mental effort to keep both items floating as Molly raced forward and dragged the woman back towards him. Sherlock collapsed to his knees, the slab and beam crashing harmlessly to the floor.

"Sherlock!" Molly exclaimed, placing her hand on his arm.

"I'll be all right," Sherlock told her as he breathed heavily.

People shouted just down the hall, and Sherlock grabbed the unconscious woman, hauling her over his shoulder.

"Come on," Sherlock told Molly.

They made their way out of the room, and Molly led him to where she had hidden the other four hostages.

One of the men, seeing how exhausted Sherlock appeared, motioned for the woman, and Sherlock gratefully handed her over. He then led them all out of the building and towards the van that he and Molly had hidden nearby the previous day.

"Don't stop until you've gone at least five miles," Sherlock advised as he closed the back doors. "Then try to find a police station."

One of the men got into the driver's seat. "What about you two?"

"We have our own car," Molly told them through the passenger window. "We'll be all right."

"Thank you," one of the women told them.

The man started the car up and took off away from the building. Sherlock looked over at Molly as she looked back at him. Neither of them seemed able to say anything for several moments.

"You're…" Molly began in a soft voice.

"Yes," Sherlock replied.

"Die Geiseln sind weg!" a man cried out from the building.

Sherlock pulled Molly over to some crates ten feet from the building. He glanced over the crates as the area lit up with activity. Ducking back down, he looked at Molly. "Maybe we'll have this conversation later?"

More shouts started up, this time outside, as footsteps headed in their direction. Sherlock and Molly both raised a hand and swept it in front of themselves, becoming invisible. A few seconds later, guards ran around the crate and past them.

Sherlock reached out, his hand coming in contact with Molly's arm. He moved down until he had Molly's hand in his grasp. "Come on."

They took off into the night.

* * *

Half an hour later, Sherlock was driving their getaway car through the night. He had called Mycroft to tell him his men could move in, and now, the two of them were driving to the arranged safehouse.

"So…" began Molly hesitantly. "You're…"

"Yes," said Sherlock.

"Wow…" said Molly. "I never thought I'd meet a merman. They haven't been seen in centuries. Which pod did you come from?"

Sherlock frowned, unsure that he had heard her correctly. "Pod?"

"Oh, do you call it something else?" said Molly.

"Call what something else?" asked Sherlock.

"The group you come from," Molly explained. "Mermaids call it pods, but I guess mermen call it something else."

A thought occurred to him, and he looked over at Molly, stunned. "You were born this way?"

Molly's brows drew together in a confused frown. "Well, yeah. Weren't you?"

Sherlock glanced back at the road. "I've only been a merman for two months."

Molly's eyes widened. "You're a land boy?"

"Land boy?" scoffed Sherlock, unable to help himself.

"How did this happen?" she went on.

"I was on a case in America, and I chased my suspect into a cave on the night of a full moon," Sherlock told her. "He nearly knocked me unconscious into the moon pool, and when I was lucid enough to notice, the moon was overhead."

Molly's eyes were almost comically wide. "I had no idea a moon pool could transform a land person like that. I've never heard of it happening before. Then again, we are very protective of our moon pools. Perhaps there was no pod near that one."

"Tell me about these pods," Sherlock requested. "Are they family groups like whale pods? Do you grow up in the water? How are you born? Do the expectant mothers have to go on land to get rid of their tails for childbirth? How—"

"Wait a minute, wait a minute," Molly stopped him. "One question at a time."

"Do you live in the water, or does a pod go back and forth?" asked Sherlock.

"Mostly, we grow up living in the water," Molly explained. "Although, mermaid school does take frequent trips onto land so we can learn how that world works as well."

"Mermaid school?" asked Sherlock.

"It's where we're taught how to use our powers. Once we reach a certain age, we graduate. Not that there's a ceremony or anything like land people do it. Basically, you earn your moon ring."

Molly held up her right hand, and Sherlock glanced down at the silver ring with round aqua stone he had seen many times on her index finger. He had always assumed it to be a gift from a deceased relative or—worse—one of those gaudy promise rings.

"It stores moonlight," Molly explained, the fingers of her left hand brushing over it fondly. "It is the most prized possession any mermaid could have."

"Does it amplify your powers?" asked Sherlock.

Molly looked up at him, nodding. "You've guessed that our power comes from the moon?"

Sherlock nodded. "Fairly simple deduction."

"The moon ring simulates the power of the full moon. It amplifies our powers and even creates its own."

"Such as?"

"It creates legs for us," said Molly.

Sherlock frowned over at her.

"We're born as mermaids," Molly explained. "We have tails. It isn't until we start mermaid school around the age of six that our teacher uses her moon ring to give us legs. From then on, we're just like you. Dry, we have legs. Wet, we have tails."

"And you chose to live on land?" asked Sherlock.

"Once we earn our moon ring, we're given a choice to either live in the water or on land. Not that we're cut off from the other if we pick one. I live on land, but I still visit my pod frequently."

"You chose land because this world fascinated you, and your curiosity about land people led you to become a pathologist."

Molly nodded. "Any other questions?"

"May I visit the pod?"

"One day, yes," Molly replied. "We aren't prejudiced towards land people or mermen, but we are wary. I'll have to tell them about you and why I trust you first."

Sherlock gave a nod. "Fair enough."

"They'll be excited," Molly assured him. "To get to meet the first merman in centuries? Who used to be a land person, no less? They'll want to meet you soon."

Sherlock smirked a little. "Actually, I'm the second."

Molly's head whipped over to him. "Who was the first?"

Sherlock looked over at her, relishing the look of shock that was about to appear on her face. "John."

Molly's jaw dropped, causing Sherlock's smirk to grow. "John?! When?"

"When he was fourteen," Sherlock replied as he turned off the road towards the safehouse. "He transformed while on a family vacation in Ireland."

"No way…" said Molly in an amazed voice.

Sensing something there, Sherlock glanced at her. "What?"

"On the coast? Near Wicklow?"

Sherlock frowned over at her. "Yes. Your pod's moon pool?"

Molly nodded. "Every full moon, we gather in the sea off the coast, and one of us—those still in school but old enough to have some kind of grasp on our powers—guard the moon pool.

"About twenty years ago, one of the girls was spooked by noises she heard coming through the caves. She got scared and left. There wasn't anything damaged when they checked in the morning, but there was a pile of charred wood."

"John lit a fire to keep himself warm," Sherlock told her, nodding. "Why did this girl spook? Wasn't your pod used to hiding from land people?"

"No one had ever gotten that far into the caves before. Any normal person would have given up at the crevasse."

Sherlock grinned. "Except if you're a future army doctor." He pulled the car to a stop in front of the house.

"After that, we were much more careful about making sure no one got that far," Molly explained as she got out of the car. "Does John know about you?"

"Yes, I found out about him five months ago," Sherlock replied as he got out of the car as well. "He found out a few days after I returned from America. He's been especially helpful teaching me how to navigate my powers."

Molly shook her head as she headed for the house. "God, this just explains everything! I thought it was me this whole time!"

Sherlock almost froze in his steps behind her. _How could she think being a merman prevents me from returning her affections? I wasn't even a merman when he started trying to flirt. Oh, please don't let us start talking about_ _ **feelings**_ _._

He repressed the grimace at the thought of emotions as Molly turned towards him.

"The liquids in my lab have been acting up the last several weeks, but oddly enough, only when you're around," she told him.

Sherlock frowned as they stopped at the door. "They have?"

"I really should have put it together sooner, but I was so worried that it was me that I wasn't really paying attention." Molly looked up at him with a playful smile. "Any liquids stores in the lab or morgue have been bubbling and sloshing around. It wasn't until now that I realize it only happens when you get excited about a case."

Sherlock closed his eyes. "Dammit."

Molly giggled as Sherlock pulled a key out to open the door.

* * *

John stepped into his sitting room, putting his bag down by the door. "Oh, God…"

"Harry prove difficult, as usual?"

John looked up at Sherlock sitting in his armchair. "Yeah. As usual."

Sherlock gave a frown as he lowered his arms to the armrests. "Did you ever think that Harry's drinking might stem from jealousy?"

John frowned as he moved to his own armchair. "Jealousy?"

"For you," said Sherlock. At John's continued frown, he added, "Your gifts."

John stared at him for several seconds before gazing down at the floor. "That would explain a lot."

"She never tried to get to the moon pool?" asked Sherlock.

"Maybe she did but couldn't make it past the crevasse," mused John.

"Or perhaps it was more heavily guarded," Sherlock muttered.

John looked up at him, frown in place again. "Guarded?"

"Tea, John?"

John spun in his seat to see Molly moving around in the kitchen. _Shit. How much did she hear?_ "Molly…I didn't know you were here."

"I thought I would invite Molly to eat dinner with us," said Sherlock. "A thank you for helping with the case."

"You don't mind, do you, John?" said Molly, bringing two cups of tea into the sitting room.

Since she didn't seem to be acting any differently, John accepted the tea like nothing had happened. "No, not at all. How did the case go?"

"A success," said Sherlock, accepting his own tea from Molly.

"No, er…" John gave him a look as Molly went back to the kitchen, "problems?"

"Well, we did find some hostages," said Molly, grabbing her own tea and returning, sitting on a dining chair facing the fireplace. "But we got them out. Mycroft took care of the rest."

John's eyes narrowed as he stared at Molly. There was something different about her. Usually, her poorly concealed feelings for Sherlock kept her shy and meek in his presence. But she wasn't avoiding eye contact or stuttering or being shy at all. The attraction was still there, if her smiles and blushes towards Sherlock were any indication. What had happened?

"Problem, John?" asked Sherlock.

John quickly looked at him as he realized he had been staring. "No, no, just tired, I guess."

"Well, to answer your question, no, I did not have any problems," Sherlock told him. "Our secret is still safe."

John disguised the clatter of his cup in its saucer as him setting it on the table next to him, rather than that his hands were shaking. "Secret? What secret?" How he wished telepathy were one of their powers so he could tell Sherlock to shut up!

"That we're mermen," Sherlock stated simply.

John swore that he stopped breathing. Sherlock had a tendency to not notice when he left. Could he have forgotten that Molly was sitting _right there_?

"What in the world are you talking about?" asked John in a breathless voice. _Well, of course it's breathless. You've stopped breathing, remember?_

"It's okay, John," said Molly with an amused smile. "I know."

John's gaze shot over to her. "You know?"

"I know," Molly nodded. "And I will keep your secret. And I trust you'll keep mine."

"Yours?" asked John, his heart trying to recover from the shock as he tried to tell his lungs to breathe.

Molly held her hand out towards John's abandoned cup, causing the tea inside to float up into the air.

No matter what Sherlock says, John Watson absolutely DID NOT faint.

* * *

 **I know, I know. It's a very dramatic reveal for Sherlock and Molly, but it's my story, so I don't care. Plus, it'll get much more dramatic as the stories go on.**

 **FYI, the German sentence translates at "The hostages are gone!"**


End file.
